Blur correction apparatus

ABSTRACT

A blur correction apparatus includes a first fixing member, a moveable member and a second fixing member. A coil for generating a magnetic flux is arranged on the first fixing member. The movable member includes (1) an optical element, (2) a first magnet facing the coil, and (3) a second magnet arranged along a line parallel with an optical axis of the optical element and facing the first magnet, such that the first magnet is arranged between the second magnet and the coil. The movable member can move in a direction perpendicular to the optical axis. The second fixing member includes a hall element that is arranged adjacent to the second magnet. The second magnet is arranged between the first magnet and the hall element. The coil, the first magnet, the second magnet and the hall element are sequentially disposed in a line parallel with the optical axis, in this order.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/294,538 (referred to as “the '538 application” andincorporated herein by reference), filed on Jun. 3, 2014, titled “BLURCORRECTION APPARATUS” and listing Kazunori YUGE, Masaya OTA and YoshiakiSUEOKA as inventors, the '538 application claiming the benefit ofJapanese Application No.2013-118172 filed in Japan on Jun. 4, 2013, thecontents of which are incorporated herein by this reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments described herein relate generally to a blur correctionapparatus provided in an imaging device such as a digital camera.

2. Description of the Related Art

In recent years, digital cameras provided with a blur correctionapparatus for correcting image blur caused by movement of aphotographer's hand have become prevalent. Two types of blue correctiontechniques are known. In a first type of the blur correction apparatus,an image sensor is driven along a plane perpendicular to an optical axisto cancel blur. In a second type of the blur correction apparatus, alens is driven along a plane perpendicular to the optical axis to cancelblur. A VCM (voice coil motor) is generally used as the drivingmechanism of such blur correction apparatuses.

A VCM includes a magnet and coil. One of the magnet and coil is attachedto a movable frame which holds an optical member (such as an imagesensor or lens) to be driven, and the other of the magnet and coil isattached to a fixed frame which holds the movable frame such that themovable frame can move along a plane perpendicular to the optical axis.As described above, the magnet and coil may be attached to either of themovable frame or fixed frame, with one of the magnet or coil beingattached to the movable frame, and the other of the magnet or coil beingattached to the fixed frame.

Additionally, a hall element is attached to either of the movable frameor fixed frame so that a position of the movable frame relative to thefixed frame can be detected and a magnet for the position detection isattached to the other of the movable frame or fixed frame. The hallelement and magnet for position detection may be basically attached toeither of the movable frame or fixed frame. The magnet for driving theVCM may also be used for position detection.

According to Japanese Patent Application Laid-Open No. 2008-26882, astructure is disclosed where a magnet for driving is attached to a fixedframe, a coil for driving is attached to a movable frame opposite to themagnet for driving, a magnet for position detection is attached to themovable frame deviated from the coil for driving and a hall element isattached to the fixed frame opposite to the magnet for driving.

SUMMARY OF THE INVENTION

A blur correction apparatus according to an example embodimentconsistent with the present invention includes a first fixing member onwhich a coil is disposed; a movable member including (1) a first magnetfacing the coil, (2) a second magnet disposed adjacent to the firstmagnet, such that the first magnet is arranged between the second magnetand the coil, and (3) an optical element, wherein the movable member canmove in a direction perpendicular to an optical axis of the opticalelement relative to the first fixing member; and a second fixing memberincluding a hall element that is disposed adjacent to the second magnet.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a digital camera according to anembodiment of the present invention.

FIG. 2 is a perspective view showing a lens unit incorporated in thedigital camera of FIG. 1.

FIG. 3 is a cross-sectional view obtained by cutting the lens unit ofFIG. 2 along an optical axis.

FIG. 4 is a perspective view showing a blur correction unit according tothe embodiment incorporated in the lens unit of FIG. 2.

FIG. 5 is an exploded perspective view of the blur correction unit ofFIG. 4.

FIG. 6 is a sectional view obtained by cutting the blur correction unitof FIG. 4 along line F6-F6.

FIG. 7 is a sectional view obtained by cutting the blur correction unitof FIG. 4 along line F7-F7.

FIG. 8 is an illustration showing a movable body of FIG. 5 from anobject side.

FIG. 9 is an illustration showing the movable body of FIG. 8 from animage sensor.

FIG. 10(a) is an illustration showing an assembly from the object sidewherein the movable body of FIG. 8 is connected to a fixed barrel. FIG.10 (b) is a partial magnified view of a principal part of FIG. 10 (a).

FIG. 11 is a sectional view obtained by cutting the assembly of FIG.10(a) along line F11-F11.

FIG. 12 is a block diagram showing a control system which controls theblur correction unit of FIG. 4.

FIG. 13 is a layout indicating a relationship of components incorporatedin the blur correction unit of FIG. 4 along the optical axis.

FIG. 14 is a graph showing a driving force and magnitude of the magneticflux when a distance ‘A’ of FIG. 13 is changed.

FIG. 15 is a graph showing driving frequency characteristics of hallelement output of the blur correction unit which does not include asecond magnet.

FIG. 16 is a graph showing driving frequency characteristics of hallelement output of the blur correction unit according to the embodimentwhich includes a second magnet.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Example embodiments consistent with the present invention will bedescribed in detail below with reference to the drawings. In each of thedrawings for use in the following description, each of components isshown different scales according to each of the components in order tomake each component recognizable in the drawings. Accordingly, thepresent invention is not limited only to the numbers and quantities ofthe components, the shapes of the components, the ratios of the sizes ofthe components and the relative positional relations of the respectivecomponents which are illustrated in these drawings.

In the following description, a direction from a camera body 200 to theobject (not shown) is referred to as ‘frontward’ or ‘forward’ while adirection opposite thereto is referred to as ‘backward’ or ‘rearward’.An axis which coincides with an optical axis O of an optical systemformed of a lens unit 100 is defined as ‘Z axis’, and two axesperpendicular to each other in a plane perpendicular to the Z axis aredefined as ‘X axis’ (an axis in the horizontal direction) and ‘Y axis’(an axis in the vertical direction), respectively. The X axis, Y axisand Z axis are shown in the drawings.

FIG. 1 is a perspective view showing a digital camera 10 according to anexample embodiment consistent with the present invention. FIG. 2 is aperspective view showing the lens unit 100 incorporated in the digitalcamera 10 of FIG. 1. FIG. 3 is a cross-sectional view obtained bycutting the lens unit 100 of FIG. 2 along the optical axis O. As shownin the diagrams, the digital camera 10 is provided with a camera body200 and the lens unit 100 which can be projected from and retracted intothe camera body 200.

The lens unit 100 is built in the camera body 200 such that a secondlens barrel 102 and a third lens barrel 103 of the lens unit 100 can beprojected from a front face of the camera body 200. That is, a firstlens barrel 101 of the lens unit 100 is provided within the camera body200. When the lens unit 100 is in a retracted state, the second lensbarrel 102 and the third lens barrel 103 are mostly housed within acentral void defined by the first lens barrel 101, which is providedwithin the camera body 200. Therefore, in the retracted state, thesecond lens barrel 102 and the third lens barrel 103 do not project outfrom the front of the camera body. FIGS. 2 and 3 show an extended stateof the lens unit 100.

The camera body 200 is provided with a housing 201 having asubstantially rectangular box shape. The housing 201 is provided with acontrol panel 202, zoom lever 203, flash 204, self-timer signal 205,remote control receiving window 206, release switch 207, power switch208 and finder 209. A rear surface (not shown) of the camera body 200 isprovided with a panel for displaying an image obtained by photographingan object, photographing information, and/or images captured in a liveview operation.

When a main power supply is turned on, each lens barrel (describedlater) moves to a photograph ready position. At the photograph readyposition, a focal point is matched to a wide end or around the wide end.If a user operates the zoom lever 203 in this state, a zoom motor 104(FIG. 2) of the lens unit 100 is driven. As a result, a fourth lensbarrel 105 is rotated via a zoom gear (not shown). The fourth lensbarrel 105 is engaged with a helicoid formed on the first lens barrel101 and is projected from the first lens barrel 101 while rotating withrespect to the first lens barrel 101. At the same time, the second lensbarrel 102 moves in a straight line and is projected in conjunction withthe projection of the fourth lens barrel 105. A cam groove (not shown),which is coupled to the third lens barrel 103 by a cam mechanism, isformed outside the fourth lens barrel 105. The third lens barrel 103moves in a straight line by rotation of the fourth lens barrel 105 andis projected more towards the object than the second lens barrel 102.FIG. 3 shows a state in which the lens unit 100 is extended to atelephoto end. In a retracted state, the second lens barrel 102 and thethird lens barrel 103 are accommodated in the first lens barrel 101.

As shown in FIG. 3, the lens unit 100 is provided with a first lensgroup 111, a second lens group 112, a third lens group 113, a fourthlens group 114, and a fifth lens group 115, which move along the opticalaxis O apart from each other. Each lens group is fixed to a lens frameand driven in units of the lens frames. The third lens group 113 isdisposed in a lens frame (not shown) which moves in a straight linealong the optical axis O in conjunction with rotation of the fourth lensbarrel 105. The first lens group 111 and the second lens group 112 aredisposed in lens frames (not numbered) which move in conjunction withrotation of the above-described fourth lens barrel 105. That is, theymove in a straight line along the optical axis O in conjunction withrotation and movement in a straight line of the fourth lens barrel 105.The fourth lens group 114 and the fifth lens group 115 are movable alongthe optical axis O by another motor (not shown). The third lens group113 is driven to correct blur. The fourth lens group 114 is driven basedon object information to perform focusing by auto-focus.

At the time of photographing, object light (not shown) passes throughthe first to fifth lens groups (111 to 115) and is formed on an imagesensor 120. At that time, each lens group of 111 to 115 is disposed at aprescribed position along the optical axis direction based on an amountof operation of the zoom lever 203 and the focal length of the object byauto-focus. Then the object image is formed on the image sensor 120 witha desired magnification. The image sensor 120 is fixedly provided at arear end of the first lens barrel. An alternative embodiment consistentwith the invention has a removable lens unit, and the image sensor isprovided in the camera body. In such an alternative embodiment, ablurring correction unit could be provided in the lens unit (e.g., toshift a lens group in order to provide blur correction), or in thecamera (e.g., to shift the imaging unit to provide blur correction).

FIG. 4 is a perspective view showing a blur correction unit 1incorporated in the lens unit 100 of FIG. 2. FIG. 5 is an explodedperspective view of the blur correction unit 1 of FIG. 4. The blurcorrection unit 1 includes the above-described third lens group 113, andimage blur can be corrected by moving the third lens group 113 along an‘XY’ plane perpendicular to the optical axis O.

As shown in FIG. 5, the blur correction unit 1 includes a fixed barrel2, a movable body 4 which holds the third lens group 113 (opticalmember) and a shutter unit 6. The third lens group 113 is fixed to themovable body 4 such that its movement corresponds to that of themoveable body. More specifically, as shown in FIG. 6, the third lensgroup 113 is fixed to a frame 41 of the movable body 4. The shutter unit6 functions as a first fixing member. The fixed barrel 2 functions as asecond fixing member. The movable body 4 functions as a movable member.That is, the fixed barrel 2 is fixed to the first lens barrel 101 of thelens unit 100 and the shutter unit 6 is fixed to in front of the fixedbarrel 2.

Two hall elements 13 and 14 are fixedly attached to a frame 21 of thefixed barrel 2. (See FIGS. 6 and 7.) The hall element 13 is a detectionmeans which detects movement of the movable body 4 in the X axisdirection. The hall element 14 is a detection means which detectsmovement of the movable body 4 in the Y axis direction. Two coils 15 and16 are fixedly provided on the shutter unit 6, opposite to the hallelements 13 and 14, respectively, in the optical axis direction. In anassembled state of the blur correction unit 1 shown in FIG. 4, the twohall elements 13 and 14 are disposed far away enough from the coils 15and 16, respectively, in the optical axis direction so as not to receiveany influence of a respective magnetic field from the two coils 15 and16. More specifically, the magnitude and direction of the current to besupplied to the coils 15 and 16 is changed frequently in order to movethe movable body 4 frequently to eliminate or reduce blur. As a result,the magnitude of a generated magnetic field also changes frequently. Thetwo hall elements 13 and 14 are used to detect the magnetic fields ofthe respective second magnets 17 and 18, whose positions change. If adistance between the coils 15 and 16 and the hall elements 13 and 14,respectively, is short at this time, the magnetic field (which changesfrequently) leaks, and is detected by the hall elements 13 and 14. Thatis, the influence of the magnetic fields for the coils 15 and 16 on therespective hall elements 13 and 14 can become large if the spacing istoo small. Accordingly, the hall elements 13 and 14 are disposed faraway enough from the coils 15 and 16, respectively, in the optical axisdirection. Although there is slight influence of the first magnets 11and 12 and the second magnets 17 and 18, this is not a problem becausethe first magnets 11 and 12 are disposed far away enough from the coils15 and 16 so as not to generate an influence on the hall elements. (SeeFIGS. 13 and 14), and the magnetic forces of the second magnets 17 and18 are weak.

FIG. 6 is a sectional view obtained by cutting the blur correction unit1 of FIG. 4 along an ‘XZ’ plane which passes though the optical axis O.FIG. 7 is a sectional view obtained by cutting the blur correction unit1 of FIG. 4 along a ‘YZ’ plane which passes though the optical axis O.Referring to FIG. 6, a magnet 11 for driving (hereinafter referred to as‘first magnet 11’) and a magnet 17 for position detection (hereinafterreferred to as ‘second magnet 17’) are disposed between the coil 15 andthe hall element 13, but do not contact each other (in a non-contactstate). Similarly, referring to FIG. 7, a magnet 12 for driving(hereinafter referred to as ‘first magnet 12’) and a magnet 18 forposition detection (hereinafter referred to as ‘second magnet 18’) aredisposed between the coil 16 and the hall element 14, but do not contacteach other (in a non-contact state). The first magnets 11 and 12 areattached to a frame 41 of the movable body 4 on a side closer to theobject being photographed, and the second magnets 17 and 18 are attachedto the frame 41 of the movable body 4 on a side closer to the imagesensor 120. According to the example embodiment illustrated, the firstmagnets 11 and 12 and second magnets 17 and 18 are disposed such thatthere is space between them. (See FIGS. 6 and 7.)

The drive mechanism for moving the movable body 4 in the X axisdirection (FIG. 6) has basically the same configuration as that formoving the movable body 4 in the Y axis direction (FIG. 7). Therefore,only one of the drive mechanisms will be described in the following.(More specifically, the mechanism shown in FIG. 6 for movement in the Xaxis direction will be described and that of FIG. 7 will be omitted.)

The coil 15 is fixedly provided on the shutter unit 6 on a side facingthe image sensor 120. The shutter unit 6 includes a positioning boss 6 afor positioning the coil 15, and the coil 15 is attached thereto. Thus,the positioning boss 6 a positions the coil 15 on the ‘XY’ plane.

The hall element 13 is disposed at a remote position from the coil 15 inthe optical axis direction. The hall element 13 is mounted on asubstrate 22 and attached to the frame 21 of the fixed barrel 2. Thesubstrate 22 is disposed on a side of the frame 21 facing the imagesensor 120 and touches the frame 21. (As the substrate, a flexiblesubstrate can be used.)

The first magnet 11 (for driving) is fixedly provided in the frame 41 ofthe movable body 4 near and facing a side of the coil 15 facing theimage sensor 120. It is preferable to dispose the coil 15 as close tothe first magnet 11 as possible. According to the example embodimentillustrated, the magnet 11 is provided with a yoke 11 a between theframe 41 on a side away from the coil 15 (facing the image sensor 120).The yoke 11 a is not necessary and need not be included in alternativeembodiments.

The second magnet 17 (for position detection) is fixedly provided in theframe 41 of the movable body 4, apart from the first magnet 11 (and yoke11 a) and facing the object-facing side of the hall element 13. Thesecond magnet 17 applies a magnetic field that can be sensed by the hallelement 13. Consequently, the hall element 13 can detect a position ofthe movable body 4 along the X axis based on a detected strength or achange in detected strength of the magnetic field. Further, the secondmagnet 17 is magnetically coupled to the first magnet 11 and assists thesecond magnet 17 in driving the movable body 4 along the X axisdirection. Therefore the position of the second magnet 17 along theoptical axis direction is chosen so as to satisfy both positiondetection (in cooperation with the hall element 13) and drive of themovable body 4 (in cooperation with the first magnet 11). The secondmagnet 17 is arranged such that the magnetic force of the second magnet17 complements (that is, enhances) the magnetic force of the firstmagnet 11. That is, the second magnet 17 is magnetically coupled withthe first magnet 11. Consequently, the magnetic force of the secondmagnet 17 enhances the magnetic force of the first magnet 11.

As described above, the coil 15, the first magnet 11, the second magnet17, and the hall element 13 are sequentially disposed in the opticalaxis direction (Z axis direction) so that the hall element 13 may bedisposed closest to the image sensor 120. The coil 15, the first magnet11, the second magnet 17, and the hall element 13 do not touch eachother and are spaced apart from each other. The four components aredisposed such that a center of each component is on a line (not shown)parallel to the optical axis O.

As seen from FIGS. 6 to 8, each of the first magnets 11 and 12 and thesecond magnets 17 and 18 consists of two magnets which were adhered inthe optical axis direction. Each magnet (first magnet 11, 12 and secondmagnet 17, 18) has a virtual boundary line A (See, e.g., dotted lines ofFIG. 8) and virtual boundary line B (See, e.g., dotted lines of FIGS. 6and 7.). The virtual boundary line A and the virtual boundary line B₁ ofmagnet 11 are explained with reference to FIGS. 6 and 8. In FIG. 8, thevirtual boundary line A of the magnet 11 is located virtually between anN pole and an S pole, and is oriented in a direction (Y-direction) thatis perpendicular to an optical axis. Referring to FIG. 6, the virtualboundary line B₁ of the magnet 11 is oriented in a direction(Z-direction) parallel to the optical axis. Thus, the virtual boundarylines A and B₁ define a YZ plane that is parallel to an optical axis. Aspreviously described with reference to FIG. 6, two magnets areadhesively bonded so that the magnetic poles are reversed. That is,virtual line B₁ defines a boundary line between (1) an N pole and an Spole of the upper part of magnet 11, and (2) an S pole and the N pole ofthe lower part of the magnet 11. Referring now to FIG. 7, note that themagnet 12 is arranged in an orientation rotated 90 degrees from magnet11. Notice that the magnet 12 also has a virtual boundary line A asshown in FIG. 8, and a virtual boundary line B₃ as shown in FIG. 7.Together, these virtual boundary lines A and B₃ define an XZ plane thatis parallel to an optical axis. Referring to both FIGS. 6 and 7 althoughthe magnet 17 is different from the magnet 11 in size and magneticforce, and the magnet 12 is different from the magnet 18 in size andmagnetic force, the magnets 17 and 18 have (1) virtual boundary lines A(not shown) corresponding to those A of magnets 11 and 12, respectively,and (2) virtual boundary lines B₂ and B₄ corresponding to B₁ and B₃,respectively. Thus, the virtual boundary line A of the first magnet 11and the virtual boundary line A (not shown) of the second magnet line 17are located in parallelism in an optical axis direction (Z-axisdirection) and are placed in the same YZ plane. Similarly, the virtualboundary line A of the first magnet 12 and the virtual boundary line A(not shown) of the second magnet line 18 are located in parallelism inan optical axis direction (Z-axis direction) and are placed in the sameXZ plane. Further, as shown in FIG. 6, virtual boundary lines B₁ and B₂of the magnets 11 and 17, respectively, are located on the same line (orat least are parallel on a YZ plane) in an optical axis direction(Z-axis direction). Likewise, as shown in FIG. 7, virtual boundary linesB₃ and B₄ of the magnets 12 and 18, respectively, are located on thesame line (or at least are parallel on an XZ plane) in an optical axisdirection (Z-axis direction). Finally, B₁ and B₂ and B₃ and B₄ areparallel with each other in an optical axis direction.

A structure for holding the movable body 4 in a movable condition alongthe ‘XY’ plane will be described below with reference to FIGS. 8 to 11.FIG. 8 is an illustration showing the movable body 4 from the objectside. FIG. 9 is an illustration showing the movable body 4 from theimage sensor 120. FIG. 10(a) is an illustration showing an assembly 20from the object side wherein the movable body 4 is attached to the fixedbarrel 2. FIG. 10 (b) is a partial magnified view of a principal part ofthe assembly 20 of FIG. 10 (a). FIG. 11 is a sectional view obtained bycutting the assembly 20 of FIG. 10(a) along line F11-F11.

As shown in FIG. 11, a spring 31 b is provided, which connects the frame21 of the fixed barrel 2 to the frame 41 of the movable body 4 via aball 32 b. One end of the spring 31 b is connected to the frame 41 ofthe movable body 4, and another end of the spring 31 b is connected tohook 23 b at a side of the spring 31 b facing the image sensor 120 (notshown, on a lower side in the drawing). In FIG. 11, the spring 31 b isshown representatively, but actually three springs 31 a, 31 b and 31 cand three hooks 23 a, 23 b and 23 c to which the springs are connectedare provided on the frame 21 of the fixed barrel 2. Similarly threeballs 32 a, 32 b and 32 c are provided between the frame 21 of the fixedframe 2 and frame 41 of the movable body 4, and three depressions 25 a,25 b and 25 c for receiving the three balls 32 a, 32 b and 32 c,respectively, are provided. (In FIG. 11, only the depression 25 b isshown.)

As shown in FIGS. 10 (a) and (b), eight stoppers 26 a, 26 b, 26 c, 26 d,26 e, 26 f, 26 g and 26 h are provided, and project from the frame 21 ofthe fixed barrel 2 on a side facing the object. The eight stoppers 26 ato 26 h can come into contact with an edge of the frame 41 of themovable body 4 thereby limiting its movement and defining a movablerange of the movable body 4 along the ‘XTY’ plane.

The movable body 4 includes the frame 41 and the third lens group 113 isattached at a center thereof As shown in FIG. 8, the two first magnets11 and 12 are provided in the frame 41 on a side facing the object.Referring back to FIGS. 6 and 7, these two first magnets 11 and 12respectively face the coils 15 and 16 provided in the shutter unit 6. Asshown in FIG. 9, the two second magnets 17 and 18 are provided in theframe 41 on a side facing the image sensor 120. Referring back to FIGS.6 and 8, these two second magnets 17 and 18 respectively face the twohall elements 13 and 14 fixedly attached to the frame 21 of the fixedbarrel 2. The second magnets 17 and 18 are smaller and weaker than thefirst magnets 11 and 12.

As shown in FIGS. 6 and 7, each of the first magnets 11 and 12 isarranged in a respective depression of the frame 41, on a closer facingthe object. Referring to FIG. 8, each of the first magnets 11 and 12 isfixed within the respective depression by an adhesive agent 42 providedat three peripheral sides. Referring to FIGS. 7 and 9, each of thesecond magnets 17 and 18 is fixed (e.g., by an adhesive agent) to an endof a respective projecting portion 41 a projecting towards the imagesensor 120. The movable body 4 is basically arranged such that theoptical axis O of the lens unit 100 passes through the center of thethird lens group 113.

Additionally, the frame 41 is provided with three hooks 43 a, 43 b and43 c for attaching an end of the respective above-described springs 31a, 31 b and 31 c, and three pads 44 a, 44 b and 44 c for contacting thesurfaces of the respective three balls 32 a, 32 b and 32 c in theabove-described respective three depressions 25 a, 25 b and 25 c. Asshown in FIG. 9, the three pads 44 a, 44 b and 44 c are provided on theframe 41 on a side facing the image sensor 120.

That is, the three hooks 43 a, 43 b and 43 c are provided opposite tothe three hooks 23 a, 23 b and 23 c. respectively, of the fixed barrel 2in the optical axis direction, and the three pads 44 a, 44 b and 44 care provided opposite to the three depressions 25 a, 25 b and 25 c,respectively, of the fixed barrel 2 in the optical axis direction.

As shown in FIG. 10 (a), the movable body 4 is arranged inside the fixedbarrel 2, and a peripheral edge portion of the frame 41 of the movablebody 4 is arranged inside the fixed barrel 2, apart from the eightstoppers 26 a, 26 b, 26 c, 26 d, 26 e, 26 f, 26 g and 26 h projectingfrom the frame 21 of the fixed barrel 2. The eight stoppers include thefour stoppers 26 a, 26 b, 26 e and 26 f for limiting the movement of themovable body 4 along the X axis (to left/right in FIG. 10(a)) and fourstoppers 26 c, 26 d, 26 g and 26 h for limiting the movement of themovable body 4 along the Y axis (to the vertical direction in FIG.10(a)). The eight stoppers limit movement of the movable body 4 withinthe XY plane, thereby defining the movable range of the movable body 4within the ‘XY’ plane.

More specifically, as a structure around the two stoppers 26 g and 26 his representatively shown in FIG. 10 (b), the frame 41 of the movablebody 4 is provided with small protrusions 41 b which project towardseach facing stopper at the periphery. There is slight space between theprotrusion 41 b of the frame 4 and facing stopper 26 g (or 26 h). Withspace between the peripheral edge portion and each stopper (26 a to 26h), the movable body 4 can move along the ‘XY’ plane along the Y axis.

As shown in FIG. 11, representative spring 31 b is arranged between, andattached to, the hook 43 b provided in the frame 41 of the movable body4 and the hook 23 b provided in the frame 21 of the fixed barrel 2. InFIG. 11, the spring 31 b is in a slightly stretched state. The ball 32 bis arranged inside the depression 25 b provided in the frame 21 of thefixed barrel 2. A surface of the ball 32 b contacts the pad 44 bprovided on the frame 41 of the movable body 4. That is, the ball 32 bis sandwiched between the depression 25 b and pad 44 b, and due toresilience of the spring 31 b, the ball 32 b is pressed from both sides.

Although not shown, similarly the ball 32 a is arranged inside thedepression 25 a provided in the frame of the fixed barrel 2 and thespring 31 a is arranged between, and attached to, the hook 43 a providedin the frame 41 of the movable body 4 and the hook 23 a provided in theframe 21 of the fixed barrel 2. Additionally, the ball 32 c is arrangedinside the depression 25 c provided in the frame of the fixed barrel 2and the spring 31 c is arranged between, and attached to, the hook 43 cprovided in the frame 41 of the movable body 4 and the hook 23 cprovided in the frame 21 of the fixed barrel 2.

The fixed barrel 2 and movable body 4 do not contact each other, thoughthey are indirectly connected via the three springs 31 a, 31 b and 31 cand three balls 32 a, 32 b and 32 c. Therefore the movable body 4 issupported in a floating manner by the frame 21 of the fixed barrel 2.That is, the movable body 4 can move relative to the fixed barrel 2along the ‘XY’ plane.

Referring back to FIGS. 6 and 7, a slight space is provided between thehall elements 13 and 14 attached to the frame 21 of the fixed barrel 2and the second magnets 17 and 18, respectively. Similarly, a slightspace is provided between the coils 15 and 16 attached to the shutterunit 6 and the first magnets 11 and 12, respectively. As a result, themovable body 4 can move without these components contacting each other.That is, by passing electrical currents through the coils 15 and 16 fordriving, a magnetic field is generated by each coil depending on adirection and magnitude of the respective current. Consequently, themovable body 4 can move along the ‘XY’ plane.

FIG. 12 is a block diagram showing a control system which controls themovement of the above-described blur correction unit 1. Outputs of thetwo hall elements 13 and 14, which collectively detect the position ofthe movable body 4 along the ‘XY’ plane, provides signals to acontroller 300 (control unit) which controls an operation of the blurcorrection unit 1. More specifically, the hall element 13 shown in FIG.6 detects a magnetic field indicative of the position of the movablebody 4 along the X axis direction, and outputs a corresponding signal,and the hall element 14 shown in FIG. 7 detects a magnetic fieldindicative of the position of the movable body 4 along the Y axisdirection, and outputs a corresponding signal.

Further, two gyro sensors 302 and 304 (detecting unit) which detect blurof the digital camera 10 due to shaking, provide signals to thecontroller 300. When the optical axis of the digital camera 10 is shakenalong the ‘XZ’ plane and blur occurs in a yaw direction, the gyro sensor302 detects acceleration in the yaw direction, and outputs acorresponding signal. When the optical axis of the digital camera 10 isshaken along the ‘YZ’ plane and blur occurs in a pitch direction, thegyro sensor 304 detects acceleration in the pitch direction, and outputsa corresponding signal.

Further, the above-descried coils 15 and 16, which generate magneticfields to drive the movable body 4, are connected to the controller 300.The controller 300 controls an amount and direction of currents flowingto the coils 15 and 16 based on respective output signals from the twohall elements 13 and 14 and the two gyro sensors 302 and 304 so thatblur of the digital camera 10 can be corrected. The blur correction unit1 which includes the structure of the control system is one of theexample embodiments of the blur correction apparatus according to thepresent invention.

A blur correction operation by the blur correction apparatus of theabove-described structure will be described below. The controller 300sets the amount and direction of currents flowing to the coils 15 and 16so as to position the optical axes O of the third lens group 113 and thelens unit 100 in a coaxial configuration by supplying electric currentto the two coils 15 and 16 simultaneously with start of control.Accordingly, the movable body 4 can remain in a neutral position (thatis, a position in which the optical axes O of the third lens group 113is coaxial with that of the lens unit 100).

When photographing starts, for example, in this state, the controller300 detects the amount of blur based on the output from the two gyrosensors 302 and 304 and detects position information of the movable body4 based on the output from the two hall elements 13 and 14. Then acorrection amount is calculated based on the detection results. Based onthe calculated correction amount, the controller 300 controls the amountand direction of currents flowing to the coils 15 and 16 to move movableframe 4 holding the third lens group 113 such that blur is corrected.

Effects of the above-described embodiment will be described below byfocusing on the drive mechanism for driving the movable body 4 in the Xaxis direction (FIG. 6). If an electrical current is passed through acoil, a magnetic flux is generated depending on an amount of current andnumber of turns of the coil. As described above, if the distance betweenthe hall element 13 and the coil 15 is shorter than the predeterminedamount, or if the hall element 13 is set at a position where the hallelement 13 is influenced by the coil 15, magnetic flux of the coil 15becomes leakage magnetic flux, and as a result, the hall element 13detects the leakage magnetic flux as a noise.

On the other hand, according to the example embodiment of FIG. 6, thefirst magnet 11 for driving and the second magnet 17 for positiondetection are arranged so as to overlap with each other along the Z axiswhich is parallel to the optical axis O, and perpendicular to a drivingdirection of the movable body 4. Accordingly, a large enough magneticflux necessary for driving can be applied to the coil 15. Further, themagnetic flux detected by the hall element due to the position of thesecond magnet 17 is large enough compared to noises caused by themagnetic flux created by the coil 15. Consequently, a driving force andacceleration relative to the movable body 4 can be increased. Thisincrease improves the efficacy of blur correction. Further, an S/N(signal-to-noise) ratio of position detection of the movable body 4 canbe increased. Accordingly, accuracy of position control can besignificantly improved.

Especially, according to the example embodiment, the second magnet 17for position detection both (1) operates in collaboration with the hallelement 13 to detect the position of the movable body 4 along the Xaxis, and (2) is magnetically coupled to the magnet 11 which improvesdriving of the movable body 4 drive along the X axis. Accordingly, thedriving force can be increased compared to a case in which the secondmagnet is not provided. When the second magnet is provided, it ispreferable to arrange the first and second magnets close to each otherin order to increase acceleration.

However, when the second magnet 17 is located too close to the firstmagnet 11, the accuracy of position detection is decreased. Morespecifically, in such a state, when the movable member 4 is driven so asto be moved largely, the hall element 13 can detect the magnetic forceof the second magnet 17 because the magnetic force of the second magnet17 is very small and the output is small, but a range of the outputvalue becomes large. However, in the case where the movable member 4 isdriven so as to be moved in such a way as to oscillate, the output valueof hall element 13 does not change. Accordingly the hall element 13cannot detect magnetic force change of the second magnet 17 in such acase. That is, it is necessary to adjust the position of the secondmagnet 17 along the optical axis direction properly so as to both (1)assist the movable body 4 drive and (2) accurately detect the positionof the movable body 4 with the hall element 13.

For an example, consider a case in which the second magnet 17 is notprovided. The first magnet 11 needs to be located close to the coil 15in order to generate an enough driving force for driving the movablebody 4. Additionally, the first magnet 11 needs to be located close tothe hall element 13 in order to apply an enough magnetic field for thehall element 13 to be able to detect position. Further, the hall element13 needs to be located away from the coil 15; otherwise accuracy ofposition detection be decreased due to effects of the magnetic fieldgenerated from the coil 15 (i.e., due to noise).That is, if the secondmagnet 17 is not provided, it is necessary to increase thickness of thefirst magnet 11 in the optical axis direction in order to satisfy theabove-described conditions. In this case, a size of the first magnet 11will become large and the movable body 4 will become heavy. Thisincreased weight increases inertia and consequently, enough accelerationcannot be obtained for drive-controlling the movable body 4.

To solve the above-described problems, according to the exampleembodiment, the second magnet 17 for position detection is providedbetween the first magnet 11 and the hall element 13. A proper locationof the second magnet 17 along the optical axis direction will bedescribed below with reference to FIGS. 13 and 14.

FIG. 13 schematically shows a positional relationship along the opticalaxis direction between the coil 15, first magnet 11, second magnet 17and hall element 13. FIG. 14 shows a relationship between the drivingforce applied to the movable body 4 and the magnitude of the magneticflux generated at the coil and detected by the hall element 13 inchanging a distance ‘A’. The distance A is a distance between a lowersurface of the coil 15 (a side facing the image sensor 120 (not shown)provided underside of the drawing) and an upper side of the second coil17 (a side facing the object and opposite to the image sensor 120 (notshown)) when distances between the coil 15 and the first magnet 11 andbetween the hall element 13 and second coil 17 are constant.

Variations of the driving force will be described first. As shown inFIG. 14, the driving force is the largest when the distance ‘A’ is thesmallest (that is, when the second magnet 17 touches the first magnet11). If the distance between the second magnet 17 and the first magnet11 is gradually decreased, the driving force is reduced, as indicated bythe gentle curve. When the distance ‘A’ value reaches ‘A2’ (where themagnetic force from the second magnet 17 does not apply to the coil 15),the driving force is generated by only the first magnet 11 and remainsconstant. At the position where the distance between the first magnet 11and the second magnet 17 reaches ‘A2’, the driving force for driving themoveable member 4 depends on only the magnetic force from first magnet11. At the position where the distance between the first magnet 11 andthe second magnet 17 reaches ‘A1’, sensitivity (db) is constant. In thepresent embodiment, as shown in FIG. 16, the (db) remains at about ‘−60’when frequency is more than 1 kHz. It is noted that the value is notnecessary ‘−60’. As seen from FIG. 15, sensitivity should be low enoughnot to be ‘0’ even if a gain is increased greatly.

Variations of the magnetic flux which is generated by the coil 15 andpasses through the hall element 13 will now be described. The magneticflux of the coil 15, which is noise not relevant to the positiondetection by the hall element 13, gradually decreases as the distance‘A’ increases. For highly accurate position detection, a smallermagnetic flux (noise) of the coil 15 which passes through the hallelement 13 may be acceptable if it does not exert an undue influence onposition detection. It is preferable that the distance ‘A’ be no lessthan ‘A1’ such that the magnetic flux (noise) is at or below anacceptable level. As should be appreciated from the foregoing, settingthe distance ‘A’ between the distance ‘A2’ which the second magnet 17can be effective on for a driving force of a VCM and the distance ‘A1’where accuracy of position detection by the hall element 13 is notunduly affected enables the driving force of a VCM to be increased andwithout adversely affecting the accuracy of position detection.

FIG. 15 is a graph showing driving frequency characteristics of hallelement output of an example blur correction unit which does not includethe second magnet 17. FIG. 16 is a graph showing driving frequencycharacteristics of hall element output of the blur correction unitaccording to the example embodiment which includes the magnet 17.

As shown in the graphs, increase in sensitivity ‘M’ due to that themagnetic flux generated by the coil 15 has been detected by the hallelement 13 is seen, whether the second magnet 17 is provided or not.More specifically, the leakage magnetic flux caused by the coil 15 isundesirable for position detection by the hall element 13. That is, theleakage magnetic flux caused by the coil 15 is noise to the hall element11. The second magnet 17 is placed at the position where (1) the hallelement 13 is not affected by this noise, and (2) it contributes to thedriving force. However, according to the embodiment where the secondmagnet 17 is provided, the increase in sensitivity ‘M’ is lower than acase where the second magnet 17 is not provided. The larger the increasein sensitivity becomes, the narrower sensitivity frequency bandwidthbecomes. As a result, stop accuracy (that is, the accuracy to stop themoveable body 4 at a desired position) is reduced, for example. That is,it is advantageous to provide the second magnet 17 like the embodimentfor controlling the VCM, too.

The invention is not limited to the embodiments described above, andvarious modifications and applications can be carried out within therange without departing from the gist of the invention as a matter ofcourse. In the above-described example embodiment(s), for example, eachmagnet is disposed so that the virtual boundaries (line A) of magneticpoles of the first magnet 11 (12) for driving and the second magnet 17(18) for position detection can coincide along the driving direction ofthe movable body 4. However, the virtual boundaries (line A) of magneticpoles need not always coincide in an optical axis direction.

Also, in the above-described example embodiment(s), the third lens groupwas described as an example of an optical member as an object to bedriven for blur correction, but the present invention is not limited tothis. For example, in an alternative example embodiment, the imagesensor 120 may be used as an optical member to be driven along the ‘XY’plane for blur correction.

Also, in the above-described example embodiment(s), there is spacebetween the first magnets 11 and 12 for driving and the respectivesecond magnets 17 and 18 for position detection. However, in analternative example embodiment, the first magnet may touch the secondmagnet, without space between the magnets.

As described above, according to the example embodiment(s), the movablebody 4 which holds the lens group 113, the first magnets 11,12 fordriving which are provided on the movable body, the fixed barrel 2 whichholds the movable body 4 in a movable condition in the directionperpendicular to the optical axis O of the lens group, the coils 15,16which are provided near and facing a side of the first magnets facingthe object, the hall elements 13,14 which are provided facing the firstmagnets 11,12 and apart a certain distance from the coils 15,16, and thesecond magnets 17,18 for position detection which are provided facingthe hall elements 13,14, between the first magnets 11.12 and the hallelements 13,14 in the movable body 4 are included so that the blurcorrection apparatus can reduce the noises due to influences of themagnetic flux on the hall elements 13,14 and increase the driving forceand acceleration without using a larger magnet, when correcting blur.

The present invention is not limited to the embodiments described above,and various modifications and applications can be carried out within therange without departing from the gist of the invention as a matter ofcourse. Further, the above described embodiments include the inventionsat various stages, and various inventions can be extracted bycombinations, which will be apparent to those skilled in the art, of aplurality of constituent features disclosed. For example, even ifseveral constituent features are removed from all the constituentfeatures shown in the above described respective example embodiments, aconfiguration from which the constituent features are removed can beextracted as the invention provided that the resulting embodiment cansolve one or more of the problems addressed above. The invention is notlimited by a specific example embodiment.

What is claimed is:
 1. A blur correction apparatus comprising: a) afirst fixing member on which a coil for generating a magnetic flux isarranged; b) a movable member including 1) an optical element, 2) afirst magnet facing the coil, and 3) a second magnet arranged adjacentto the first magnet, such that the first magnet is arranged between thesecond magnet and the coil, wherein the movable member can move in adirection perpendicular to an optical axis of the optical elementrelative to the first fixing member; and c) a second fixing memberincluding a hall element that is arranged adjacent to the second magnetsuch that the second magnet is arranged between the first magnet and thehall element, wherein the coil, the first magnet, the second magnet andthe hall element are sequentially disposed in a line parallel with theoptical axis, in this order.
 2. The blur correction apparatus accordingto claim 1 wherein the first magnet and the second magnet are positionedon the moveable member such that they strengthen magnetic forces in eachother.
 3. The blur correction apparatus according to claim 1 wherein avirtual boundary line separating poles of the first magnet and a virtualboundary line separating poles of the second magnet are located inparallel in the optical axis direction of the optical member.
 4. Theblur correction apparatus according to claim 1 wherein a magnetic forceof the second magnet is weaker than that of the first magnet.
 5. Theblur correction apparatus according to claim 3 wherein a center of thehall element and the boundaries of magnetic poles are coplanar in astate in which no current passes through the coil.
 6. The blurcorrection apparatus according to claim 1 wherein the first magnet andthe second magnet are spaced apart at a distance at which (1) the secondmagnet contributes to a driving force generated due to magnetic fluxprovided from the coil and (2) accuracy of position detection by thehall element is not affected by the magnetic flux.
 7. The blurcorrection apparatus according to claim 1 wherein the first fixingmember is a shutter unit.
 8. The blur correction apparatus according toclaim 7 wherein the second fixing member is a lens barrel.
 9. The blurcorrection apparatus according to claim 1 wherein the optical element isa lens group of a lens barrel.
 10. The blur correction apparatusaccording to claim 1 wherein the optical element is an image sensor. 11.Apparatus comprising: a) a first member including a coil for generatingmagnetic flux; b) a second member including a hall element; c) a thirdmember moveable relative to the first and second members, andincluding 1) an optical element, 2) a first magnet facing the coil, and3) a second magnet arranged adjacent to the first magnet, such that thefirst magnet is arranged between the second magnet and the coil, andsuch that the second magnet is arranged between the first magnet and thehall element; and d) a blur correction controller adapted to 1) receivea first input indicative of blur due to shaking, 2) receive a secondinput indicative of magnetic flux detected by the hall element, 3)determine a blur correction value based on the first and second inputsreceived, and 4) provide an output, based on the determined blurcorrection value, to induce providing a controlled current through thecoil, wherein, responsive to current flowing through the coil, the firstand second magnets cause the third member to move relative to the firstmember in a direction perpendicular to an optical axis of the opticalelement.
 12. The apparatus of claim 11 wherein the optical element is animage sensor.
 13. The apparatus of claim 11 wherein the optical elementis a lens group.
 14. The apparatus of claim 11 wherein the hall elementis spaced away from the coil such that noise due to magnetic flux fromthe coil detected by the hall element is below a predetermined value.15. The apparatus of claim 11 wherein each of the first member, secondmember and third member is part of a retractable lens barrel.
 16. Theapparatus of claim 11 wherein the second magnet is smaller and weakerthan the first magnet.
 17. Apparatus comprising: a) a first memberincluding a two coils, each for generating magnetic flux; b) a secondmember including two hall elements; c) a third member moveable relativeto the first and second members, and including 1) an optical element, 2)two first magnets, each facing a respective one of the two coils, 3) twosecond magnets, each arranged adjacent to a respective one of the twofirst magnets, such that each of the two first magnets is arrangedbetween respective ones of the two second magnets and the two coils, andsuch that each of the two second magnets is arranged between respectiveones of the two first magnets and the two hall elements; and d) a blurcorrection controller adapted to 1) receive a first input indicative ofblur due to shaking, 2) receive a second input indicative of magneticflux detected by a first one of the two hall elements, 3) receive athird input indicative of magnetic flux detected by a second one of thetwo hall elements, 3) determine two blur correction values based on thefirst, second and third inputs received, 4) provide a first output,based on a first one of the two determined blur correction values, toinduce providing a first controlled current through a first one of thetwo coils, and 5) provide a second output, based on a second one of thetwo determined blur correction values, to induce providing a secondcontrolled current through a second one of the two coils, wherein,responsive to the first and second controlled current flowing throughthe two coils, the two first magnets and the two second magnets causethe third member to move relative to the first member in a directionperpendicular to an optical axis of the optical element.
 18. Theapparatus of claim 17 wherein the optical element is an image sensor.19. The apparatus of claim 17 wherein the optical element is a lensgroup.